feat(performance): Add async utility functions and filesystem utilities

- Implemented async utilities including delay, retryWithBackoff, withTimeout, parallelLimit, debounceAsync, AsyncMutex, and CircuitBreaker.
- Created tests for async utilities to ensure functionality and reliability.
- Developed AsyncFileSystem class with methods for file and directory operations, including ensureDir, readFile, writeFile, remove, and more.
- Added tests for filesystem utilities to validate file operations and error handling.

test/core/utils/test.async-utils.ts

@@ -0,0 +1,200 @@
+import { tap, expect } from '@git.zone/tstest/tapbundle';
+import { 
+  delay, 
+  retryWithBackoff, 
+  withTimeout, 
+  parallelLimit,
+  debounceAsync,
+  AsyncMutex,
+  CircuitBreaker
+} from '../../../ts/core/utils/async-utils.js';
+
+tap.test('delay should pause execution for specified milliseconds', async () => {
+  const startTime = Date.now();
+  await delay(100);
+  const elapsed = Date.now() - startTime;
+  
+  // Allow some tolerance for timing
+  expect(elapsed).toBeGreaterThan(90);
+  expect(elapsed).toBeLessThan(150);
+});
+
+tap.test('retryWithBackoff should retry failed operations', async () => {
+  let attempts = 0;
+  const operation = async () => {
+    attempts++;
+    if (attempts < 3) {
+      throw new Error('Test error');
+    }
+    return 'success';
+  };
+  
+  const result = await retryWithBackoff(operation, {
+    maxAttempts: 3,
+    initialDelay: 10
+  });
+  
+  expect(result).toEqual('success');
+  expect(attempts).toEqual(3);
+});
+
+tap.test('retryWithBackoff should throw after max attempts', async () => {
+  let attempts = 0;
+  const operation = async () => {
+    attempts++;
+    throw new Error('Always fails');
+  };
+  
+  let error: Error | null = null;
+  try {
+    await retryWithBackoff(operation, {
+      maxAttempts: 2,
+      initialDelay: 10
+    });
+  } catch (e: any) {
+    error = e;
+  }
+  
+  expect(error).not.toBeNull();
+  expect(error?.message).toEqual('Always fails');
+  expect(attempts).toEqual(2);
+});
+
+tap.test('withTimeout should complete operations within timeout', async () => {
+  const operation = async () => {
+    await delay(50);
+    return 'completed';
+  };
+  
+  const result = await withTimeout(operation, 100);
+  expect(result).toEqual('completed');
+});
+
+tap.test('withTimeout should throw on timeout', async () => {
+  const operation = async () => {
+    await delay(200);
+    return 'never happens';
+  };
+  
+  let error: Error | null = null;
+  try {
+    await withTimeout(operation, 50);
+  } catch (e: any) {
+    error = e;
+  }
+  
+  expect(error).not.toBeNull();
+  expect(error?.message).toContain('timed out');
+});
+
+tap.test('parallelLimit should respect concurrency limit', async () => {
+  let concurrent = 0;
+  let maxConcurrent = 0;
+  
+  const items = [1, 2, 3, 4, 5, 6];
+  const operation = async (item: number) => {
+    concurrent++;
+    maxConcurrent = Math.max(maxConcurrent, concurrent);
+    await delay(50);
+    concurrent--;
+    return item * 2;
+  };
+  
+  const results = await parallelLimit(items, operation, 2);
+  
+  expect(results).toEqual([2, 4, 6, 8, 10, 12]);
+  expect(maxConcurrent).toBeLessThan(3);
+  expect(maxConcurrent).toBeGreaterThan(0);
+});
+
+tap.test('debounceAsync should debounce function calls', async () => {
+  let callCount = 0;
+  const fn = async (value: string) => {
+    callCount++;
+    return value;
+  };
+  
+  const debounced = debounceAsync(fn, 50);
+  
+  // Make multiple calls quickly
+  debounced('a');
+  debounced('b');
+  debounced('c');
+  const result = await debounced('d');
+  
+  // Wait a bit to ensure no more calls
+  await delay(100);
+  
+  expect(result).toEqual('d');
+  expect(callCount).toEqual(1); // Only the last call should execute
+});
+
+tap.test('AsyncMutex should ensure exclusive access', async () => {
+  const mutex = new AsyncMutex();
+  const results: number[] = [];
+  
+  const operation = async (value: number) => {
+    await mutex.runExclusive(async () => {
+      results.push(value);
+      await delay(10);
+      results.push(value * 10);
+    });
+  };
+  
+  // Run operations concurrently
+  await Promise.all([
+    operation(1),
+    operation(2),
+    operation(3)
+  ]);
+  
+  // Results should show sequential execution
+  expect(results).toEqual([1, 10, 2, 20, 3, 30]);
+});
+
+tap.test('CircuitBreaker should open after failures', async () => {
+  const breaker = new CircuitBreaker({
+    failureThreshold: 2,
+    resetTimeout: 100
+  });
+  
+  let attempt = 0;
+  const failingOperation = async () => {
+    attempt++;
+    throw new Error('Test failure');
+  };
+  
+  // First two failures
+  for (let i = 0; i < 2; i++) {
+    try {
+      await breaker.execute(failingOperation);
+    } catch (e) {
+      // Expected
+    }
+  }
+  
+  expect(breaker.isOpen()).toBeTrue();
+  
+  // Next attempt should fail immediately
+  let error: Error | null = null;
+  try {
+    await breaker.execute(failingOperation);
+  } catch (e: any) {
+    error = e;
+  }
+  
+  expect(error?.message).toEqual('Circuit breaker is open');
+  expect(attempt).toEqual(2); // Operation not called when circuit is open
+  
+  // Wait for reset timeout
+  await delay(150);
+  
+  // Circuit should be half-open now, allowing one attempt
+  const successOperation = async () => 'success';
+  const result = await breaker.execute(successOperation);
+  
+  expect(result).toEqual('success');
+  expect(breaker.getState()).toEqual('closed');
+});
+
+tap.start();

test/core/utils/test.fs-utils.ts

@@ -0,0 +1,185 @@
+import { tap, expect } from '@git.zone/tstest/tapbundle';
+import * as path from 'path';
+import { AsyncFileSystem } from '../../../ts/core/utils/fs-utils.js';
+
+// Use a temporary directory for tests
+const testDir = path.join(process.cwd(), '.nogit', 'test-fs-utils');
+const testFile = path.join(testDir, 'test.txt');
+const testJsonFile = path.join(testDir, 'test.json');
+
+tap.test('should create and check directory existence', async () => {
+  // Ensure directory
+  await AsyncFileSystem.ensureDir(testDir);
+  
+  // Check it exists
+  const exists = await AsyncFileSystem.exists(testDir);
+  expect(exists).toBeTrue();
+  
+  // Check it's a directory
+  const isDir = await AsyncFileSystem.isDirectory(testDir);
+  expect(isDir).toBeTrue();
+});
+
+tap.test('should write and read text files', async () => {
+  const testContent = 'Hello, async filesystem!';
+  
+  // Write file
+  await AsyncFileSystem.writeFile(testFile, testContent);
+  
+  // Check file exists
+  const exists = await AsyncFileSystem.exists(testFile);
+  expect(exists).toBeTrue();
+  
+  // Read file
+  const content = await AsyncFileSystem.readFile(testFile);
+  expect(content).toEqual(testContent);
+  
+  // Check it's a file
+  const isFile = await AsyncFileSystem.isFile(testFile);
+  expect(isFile).toBeTrue();
+});
+
+tap.test('should write and read JSON files', async () => {
+  const testData = {
+    name: 'Test',
+    value: 42,
+    nested: {
+      array: [1, 2, 3]
+    }
+  };
+  
+  // Write JSON
+  await AsyncFileSystem.writeJSON(testJsonFile, testData);
+  
+  // Read JSON
+  const readData = await AsyncFileSystem.readJSON(testJsonFile);
+  expect(readData).toEqual(testData);
+});
+
+tap.test('should copy files', async () => {
+  const copyFile = path.join(testDir, 'copy.txt');
+  
+  // Copy file
+  await AsyncFileSystem.copyFile(testFile, copyFile);
+  
+  // Check copy exists
+  const exists = await AsyncFileSystem.exists(copyFile);
+  expect(exists).toBeTrue();
+  
+  // Check content matches
+  const content = await AsyncFileSystem.readFile(copyFile);
+  const originalContent = await AsyncFileSystem.readFile(testFile);
+  expect(content).toEqual(originalContent);
+});
+
+tap.test('should move files', async () => {
+  const moveFile = path.join(testDir, 'moved.txt');
+  const copyFile = path.join(testDir, 'copy.txt');
+  
+  // Move file
+  await AsyncFileSystem.moveFile(copyFile, moveFile);
+  
+  // Check moved file exists
+  const movedExists = await AsyncFileSystem.exists(moveFile);
+  expect(movedExists).toBeTrue();
+  
+  // Check original doesn't exist
+  const originalExists = await AsyncFileSystem.exists(copyFile);
+  expect(originalExists).toBeFalse();
+});
+
+tap.test('should list files in directory', async () => {
+  const files = await AsyncFileSystem.listFiles(testDir);
+  
+  expect(files).toContain('test.txt');
+  expect(files).toContain('test.json');
+  expect(files).toContain('moved.txt');
+});
+
+tap.test('should list files with full paths', async () => {
+  const files = await AsyncFileSystem.listFilesFullPath(testDir);
+  
+  const fileNames = files.map(f => path.basename(f));
+  expect(fileNames).toContain('test.txt');
+  expect(fileNames).toContain('test.json');
+  
+  // All paths should be absolute
+  files.forEach(file => {
+    expect(path.isAbsolute(file)).toBeTrue();
+  });
+});
+
+tap.test('should get file stats', async () => {
+  const stats = await AsyncFileSystem.getStats(testFile);
+  
+  expect(stats).not.toBeNull();
+  expect(stats?.isFile()).toBeTrue();
+  expect(stats?.size).toBeGreaterThan(0);
+});
+
+tap.test('should handle non-existent files gracefully', async () => {
+  const nonExistent = path.join(testDir, 'does-not-exist.txt');
+  
+  // Check existence
+  const exists = await AsyncFileSystem.exists(nonExistent);
+  expect(exists).toBeFalse();
+  
+  // Get stats should return null
+  const stats = await AsyncFileSystem.getStats(nonExistent);
+  expect(stats).toBeNull();
+  
+  // Remove should not throw
+  await AsyncFileSystem.remove(nonExistent);
+});
+
+tap.test('should remove files', async () => {
+  // Remove a file
+  await AsyncFileSystem.remove(testFile);
+  
+  // Check it's gone
+  const exists = await AsyncFileSystem.exists(testFile);
+  expect(exists).toBeFalse();
+});
+
+tap.test('should ensure file exists', async () => {
+  const ensureFile = path.join(testDir, 'ensure.txt');
+  
+  // Ensure file
+  await AsyncFileSystem.ensureFile(ensureFile);
+  
+  // Check it exists
+  const exists = await AsyncFileSystem.exists(ensureFile);
+  expect(exists).toBeTrue();
+  
+  // Check it's empty
+  const content = await AsyncFileSystem.readFile(ensureFile);
+  expect(content).toEqual('');
+});
+
+tap.test('should recursively list files', async () => {
+  // Create subdirectory with file
+  const subDir = path.join(testDir, 'subdir');
+  const subFile = path.join(subDir, 'nested.txt');
+  
+  await AsyncFileSystem.ensureDir(subDir);
+  await AsyncFileSystem.writeFile(subFile, 'nested content');
+  
+  // List recursively
+  const files = await AsyncFileSystem.listFilesRecursive(testDir);
+  
+  // Should include files from subdirectory
+  const fileNames = files.map(f => path.relative(testDir, f));
+  expect(fileNames).toContain('test.json');
+  expect(fileNames).toContain(path.join('subdir', 'nested.txt'));
+});
+
+tap.test('should clean up test directory', async () => {
+  // Remove entire test directory
+  await AsyncFileSystem.removeDir(testDir);
+  
+  // Check it's gone
+  const exists = await AsyncFileSystem.exists(testDir);
+  expect(exists).toBeFalse();
+});
+
+tap.start();